Conventionally, in an automotive engine starter, the torque of a motor is transmitted to a pinion via a one-way clutch, for instance, of a roller clutch type, and the pinion is in turn selectively meshed with a ting gear of an engine as disclosed, for instance, in Japanese utility model laid-open publication (kokai) No. 3-41169.
According to such an engine starter, the clutch outer member of the one-way clutch surrounds the base end of the pinion support shaft which forms the clutch inner member, and the clutch outer member is integrally coupled with a torque transmitting member which is in turn coupled with an output shaft of a motor via gears. The radially central part of the torque transmitting member is provided with means for coupling with the clutch outer member while its outer circumferential surface is provided with external teeth to be coupled with the output shaft of the motor via gears.
According to such a one-way clutch, the clutch outer member inevitably involves a small eccentricity during its operation or due to a fabrication error which could affect the gear coupling with the motor output shaft, and if the eccentricity is excessive, it could not only produce noises from the gears but also could damage the gear coupling structure. Therefore, it has been necessary to machine and assemble the various component parts with a sufficient precision so that the bearings for the clutch outer member may be free from any such eccentricity as much as possible, and/or to design the gear coupling portion to have a sufficient durability. In either case, the fabrication cost and the amount of necessary work increase, and the size of the engine starter has to be increased.